Cleaning crap out of the corners of your ceiling, and out of other foreign lands in your own home, can be a lot of trouble. What's a quick-and-dirty solution? Just duct-tape some PVC pipe to your vacuum's hose and you're all set. DIY Life has the details:

To clean cobwebs off of the ceiling all you need is some duct tape and some PVC pipe! Attach a length of PVC piping to the end of the vacuum hose and seal the seam with some duct tape. Now raise the new nozzle to the ceiling and turn on the vacuum cleaner. This will easily whisk away cobwebs and dust.

It may not be the most elegant solution, but it's just right if you don't want to shell out your hard-earned cash for a proper extension.